Commercial airliners are required to meet certain noise standards such as during takeoff and landing. A large portion of the noise produced by a commercial airliner during takeoff and landing is generated by gas turbine engines commonly used on airliners. Known methods for reducing the noise level of a gas turbine engine include acoustically treating the engine inlet of the engine nacelle. In this regard, the inner barrel section of a gas turbine engine inlet may be provided with a plurality of relatively small perforations formed in the walls of the inner barrel section. The perforations absorb some of the noise that is generated by fan blades rotating at high speed at the engine inlet, and thereby reduce the overall noise output of the gas turbine engine.
Conventional methods for forming perforations in acoustic structures such as the barrel section include forming the inner wall of the barrel section as a separate component, followed by forming the perforations in the inner wall. The inner wall may then be assembled with other components that make up the barrel section, which is then assembled with the nacelle of the gas turbine engine. Unfortunately, such conventional methods for forming acoustic structures include operations that may result in the blockage of some of the perforations after the perforations have been formed.
Conventional methods for forming acoustic structures may also result in missing perforations. Such blocked perforations or missing perforations may reduce the percent-open-area (POA) of the inner wall (e.g., the total area of the perforations as a percentage of the surface area of the inner wall) which is a characteristic of acoustic structures for measuring their overall effectiveness in absorbing or attenuating noise. Furthermore, conventional methods of forming perforations in acoustic structures are time-consuming processes that add to the production schedule and cost.
As can be seen, there exists a need in the art for a system and method for forming perforations in an acoustic structure which minimizes or eliminates the occurrence of blocked or missing perforations, and which may be performed in a timely and cost-effective manner.